glsl2: Add ir_assignment::write_mask and associated methods

Replace swizzles on the LHS with additional swizzles on the RHS and a
write mask in the assignment instruction.  As part of this add
ir_assignment::set_lhs.  Ideally we'd make ir_assignment::lhs private
to prevent erroneous writes, but that would require a lot of code
butchery at this point.

Add ir_assignment constructor that takes an explicit write mask.  This
is required for ir_assignment::clone, but it can also be used in other
places.  Without this, ir_assignment clones lose their write masks,
and incorrect IR is generated in optimization passes.

Add ir_assignment::whole_variable_written method.  This method gets
the variable on the LHS if the whole variable is written or NULL
otherwise.  This is different from
ir->lhs->whole_variable_referenced() because the latter has no
knowledge of the write mask stored in the ir_assignment.

Gut all code from ir_to_mesa that handled swizzles on the LHS of
assignments.  There is probably some other refactoring that could be
done here, but that can be left for another day.

10 files changed, 199 insertions, 52 deletions

diff --git a/src/glsl/ir.cpp b/src/glsl/ir.cpp
index 79cbaa9ea0..c3bade8d54 100644
--- a/src/glsl/ir.cpp
+++ b/src/glsl/ir.cpp
@@ -22,6 +22,7 @@
  */
 #include <string.h>
 #include "main/imports.h"
+#include "main/macros.h"
 #include "ir.h"
 #include "ir_visitor.h"
 #include "glsl_types.h"
@@ -31,13 +32,121 @@ ir_rvalue::ir_rvalue()
    this->type = glsl_type::error_type;
 }
 
+/**
+ * Modify the swizzle make to move one component to another
+ *
+ * \param m    IR swizzle to be modified
+ * \param from Component in the RHS that is to be swizzled
+ * \param to   Desired swizzle location of \c from
+ */
+static void
+update_rhs_swizzle(ir_swizzle_mask &m, unsigned from, unsigned to)
+{
+   switch (to) {
+   case 0: m.x = from; break;
+   case 1: m.y = from; break;
+   case 2: m.z = from; break;
+   case 3: m.w = from; break;
+   default: assert(!"Should not get here.");
+   }
+
+   m.num_components = MAX2(m.num_components, (to + 1));
+}
+
+void
+ir_assignment::set_lhs(ir_rvalue *lhs)
+{
+   while (lhs != NULL) {
+      ir_swizzle *swiz = lhs->as_swizzle();
+
+      if (swiz == NULL)
+	 break;
+
+      unsigned write_mask = 0;
+      ir_swizzle_mask rhs_swiz = { 0, 0, 0, 0, 0, 0 };
+
+      for (unsigned i = 0; i < swiz->mask.num_components; i++) {
+	 unsigned c = 0;
+
+	 switch (i) {
+	 case 0: c = swiz->mask.x; break;
+	 case 1: c = swiz->mask.y; break;
+	 case 2: c = swiz->mask.z; break;
+	 case 3: c = swiz->mask.w; break;
+	 default: assert(!"Should not get here.");
+	 }
+
+	 write_mask |= (((this->write_mask >> i) & 1) << c);
+	 update_rhs_swizzle(rhs_swiz, i, c);
+      }
+
+      this->write_mask = write_mask;
+      lhs = swiz->val;
+
+      this->rhs = new(this) ir_swizzle(this->rhs, rhs_swiz);
+   }
+
+   assert((lhs == NULL) || lhs->as_dereference());
+
+   this->lhs = (ir_dereference *) lhs;
+}
+
+ir_variable *
+ir_assignment::whole_variable_written()
+{
+   ir_variable *v = this->lhs->whole_variable_referenced();
+
+   if (v == NULL)
+      return NULL;
+
+   if (v->type->is_scalar())
+      return v;
+
+   if (v->type->is_vector()) {
+      const unsigned mask = (1U << v->type->vector_elements) - 1;
+
+      if (mask != this->write_mask)
+	 return NULL;
+   }
+
+   /* Either all the vector components are assigned or the variable is some
+    * composite type (and the whole thing is assigned.
+    */
+   return v;
+}
+
+ir_assignment::ir_assignment(ir_dereference *lhs, ir_rvalue *rhs,
+			     ir_rvalue *condition, unsigned write_mask)
+{
+   this->ir_type = ir_type_assignment;
+   this->condition = condition;
+   this->rhs = rhs;
+   this->lhs = lhs;
+   this->write_mask = write_mask;
+}
+
 ir_assignment::ir_assignment(ir_rvalue *lhs, ir_rvalue *rhs,
 			     ir_rvalue *condition)
 {
    this->ir_type = ir_type_assignment;
-   this->lhs = lhs;
-   this->rhs = rhs;
    this->condition = condition;
+   this->rhs = rhs;
+
+   /* If the RHS is a vector type, assume that all components of the vector
+    * type are being written to the LHS.  The write mask comes from the RHS
+    * because we can have a case where the LHS is a vec4 and the RHS is a
+    * vec3.  In that case, the assignment is:
+    *
+    *     (assign (...) (xyz) (var_ref lhs) (var_ref rhs))
+    */
+   if (rhs->type->is_vector())
+      this->write_mask = (1U << rhs->type->vector_elements) - 1;
+   else if (rhs->type->is_scalar())
+      this->write_mask = 1;
+   else
+      this->write_mask = 0;
+
+   this->set_lhs(lhs);
 }
 
 
diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index f964b36083..98789503e0 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -514,6 +514,16 @@ class ir_assignment : public ir_instruction {
 public:
    ir_assignment(ir_rvalue *lhs, ir_rvalue *rhs, ir_rvalue *condition);
 
+   /**
+    * Construct an assignment with an explicit write mask
+    *
+    * \note
+    * Since a write mask is supplied, the LHS must already be a bare
+    * \c ir_dereference.  The cannot be any swizzles in the LHS.
+    */
+   ir_assignment(ir_dereference *lhs, ir_rvalue *rhs, ir_rvalue *condition,
+		 unsigned write_mask);
+
    virtual ir_assignment *clone(void *mem_ctx, struct hash_table *ht) const;
 
    virtual ir_constant *constant_expression_value();
@@ -531,9 +541,31 @@ public:
    }
 
    /**
+    * Get a whole variable written by an assignment
+    *
+    * If the LHS of the assignment writes a whole variable, the variable is
+    * returned.  Otherwise \c NULL is returned.  Examples of whole-variable
+    * assignment are:
+    *
+    *  - Assigning to a scalar
+    *  - Assigning to all components of a vector
+    *  - Whole array (or matrix) assignment
+    *  - Whole structure assignment
+    */
+   ir_variable *whole_variable_written();
+
+   /**
+    * Set the LHS of an assignment
+    */
+   void set_lhs(ir_rvalue *lhs);
+
+   /**
     * Left-hand side of the assignment.
+    *
+    * This should be treated as read only.  If you need to set the LHS of an
+    * assignment, use \c ir_assignment::set_lhs.
     */
-   ir_rvalue *lhs;
+   ir_dereference *lhs;
 
    /**
     * Value being assigned
@@ -544,6 +576,16 @@ public:
     * Optional condition for the assignment.
     */
    ir_rvalue *condition;
+
+
+   /**
+    * Component mask written
+    *
+    * For non-vector types in the LHS, this field will be zero.  For vector
+    * types, a bit will be set for each component that is written.  Note that
+    * for \c vec2 and \c vec3 types only the lower bits will ever be set.
+    */
+   unsigned write_mask:4;
 };
 
 /* Update ir_expression::num_operands() and operator_strs when
diff --git a/src/glsl/ir_clone.cpp b/src/glsl/ir_clone.cpp
index 59831834bd..0e202164b3 100644
--- a/src/glsl/ir_clone.cpp
+++ b/src/glsl/ir_clone.cpp
@@ -242,7 +242,8 @@ ir_assignment::clone(void *mem_ctx, struct hash_table *ht) const
 
    return new(mem_ctx) ir_assignment(this->lhs->clone(mem_ctx, ht),
 				     this->rhs->clone(mem_ctx, ht),
-				     new_condition);
+				     new_condition,
+				     this->write_mask);
 }
 
 ir_function *
diff --git a/src/glsl/ir_constant_variable.cpp b/src/glsl/ir_constant_variable.cpp
index 749e2cf809..1fb73e765e 100644
--- a/src/glsl/ir_constant_variable.cpp
+++ b/src/glsl/ir_constant_variable.cpp
@@ -110,7 +110,7 @@ ir_constant_variable_visitor::visit_enter(ir_assignment *ir)
 	 return visit_continue;
    }
 
-   ir_variable *var = ir->lhs->whole_variable_referenced();
+   ir_variable *var = ir->whole_variable_written();
    if (!var)
       return visit_continue;
 
diff --git a/src/glsl/ir_copy_propagation.cpp b/src/glsl/ir_copy_propagation.cpp
index 5712398732..26588a352c 100644
--- a/src/glsl/ir_copy_propagation.cpp
+++ b/src/glsl/ir_copy_propagation.cpp
@@ -224,7 +224,7 @@ add_copy(void *ctx, ir_assignment *ir, exec_list *acp)
 	 return;
    }
 
-   ir_variable *lhs_var = ir->lhs->whole_variable_referenced();
+   ir_variable *lhs_var = ir->whole_variable_written();
    ir_variable *rhs_var = ir->rhs->whole_variable_referenced();
 
    if ((lhs_var != NULL) && (rhs_var != NULL)) {
diff --git a/src/glsl/ir_dead_code_local.cpp b/src/glsl/ir_dead_code_local.cpp
index 7a44ec8a4a..b22cc558df 100644
--- a/src/glsl/ir_dead_code_local.cpp
+++ b/src/glsl/ir_dead_code_local.cpp
@@ -137,7 +137,7 @@ process_assignment(void *ctx, ir_assignment *ir, exec_list *assignments)
    }
 
    /* Now, check if we did a whole-variable assignment. */
-   if (always_assign && (ir->lhs->whole_variable_referenced() != NULL)) {
+   if (always_assign && (ir->whole_variable_written() != NULL)) {
       /* We did a whole-variable assignment.  So, any instruction in
        * the assignment list with the same LHS is dead.
        */
diff --git a/src/glsl/ir_print_visitor.cpp b/src/glsl/ir_print_visitor.cpp
index 73476e7e9b..39b11bb32c 100644
--- a/src/glsl/ir_print_visitor.cpp
+++ b/src/glsl/ir_print_visitor.cpp
@@ -296,7 +296,19 @@ void ir_print_visitor::visit(ir_assignment *ir)
    else
       printf("(constant bool (1))");
 
-   printf(" ");
+
+   char mask[5];
+   unsigned j = 0;
+
+   for (unsigned i = 0; i < 4; i++) {
+      if ((ir->write_mask & (1 << i)) != 0) {
+	 mask[j] = "xyzw"[i];
+	 j++;
+      }
+   }
+   mask[j] = '\0';
+
+   printf(" (%s) ", mask);
 
    ir->lhs->accept(this);
 
diff --git a/src/glsl/ir_tree_grafting.cpp b/src/glsl/ir_tree_grafting.cpp
index 6f62de758b..38034a6197 100644
--- a/src/glsl/ir_tree_grafting.cpp
+++ b/src/glsl/ir_tree_grafting.cpp
@@ -315,7 +315,7 @@ tree_grafting_basic_block(ir_instruction *bb_first,
       if (!assign)
 	 continue;
 
-      ir_variable *lhs_var = assign->lhs->whole_variable_referenced();
+      ir_variable *lhs_var = assign->whole_variable_written();
       if (!lhs_var)
 	 continue;
 
diff --git a/src/glsl/ir_vec_index_to_swizzle.cpp b/src/glsl/ir_vec_index_to_swizzle.cpp
index 1e170cbae6..b3de91f8ab 100644
--- a/src/glsl/ir_vec_index_to_swizzle.cpp
+++ b/src/glsl/ir_vec_index_to_swizzle.cpp
@@ -107,7 +107,7 @@ ir_vec_index_to_swizzle_visitor::visit_enter(ir_swizzle *ir)
 ir_visitor_status
 ir_vec_index_to_swizzle_visitor::visit_enter(ir_assignment *ir)
 {
-   ir->lhs = convert_vec_index_to_swizzle(ir->lhs);
+   ir->set_lhs(convert_vec_index_to_swizzle(ir->lhs));
    ir->rhs = convert_vec_index_to_swizzle(ir->rhs);
 
    return visit_continue;
diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp
index 777b4d91f4..1cec4aa621 100644
--- a/src/mesa/program/ir_to_mesa.cpp
+++ b/src/mesa/program/ir_to_mesa.cpp
@@ -356,6 +356,7 @@ ir_to_mesa_visitor::ir_to_mesa_emit_op1(ir_instruction *ir,
 					ir_to_mesa_dst_reg dst,
 					ir_to_mesa_src_reg src0)
 {
+   assert(dst.writemask != 0);
    return ir_to_mesa_emit_op3(ir, op, dst,
 			      src0, ir_to_mesa_undef, ir_to_mesa_undef);
 }
@@ -1615,21 +1616,17 @@ ir_to_mesa_visitor::visit(ir_dereference_record *ir)
  * We want to be careful in assignment setup to hit the actual storage
  * instead of potentially using a temporary like we might with the
  * ir_dereference handler.
- *
- * Thanks to ir_swizzle_swizzle, and ir_vec_index_to_swizzle, we
- * should only see potentially one variable array index of a vector,
- * and one swizzle, before getting to actual vec4 storage.  So handle
- * those, then go use ir_dereference to handle the rest.
  */
 static struct ir_to_mesa_dst_reg
-get_assignment_lhs(ir_instruction *ir, ir_to_mesa_visitor *v,
+get_assignment_lhs(ir_dereference *ir, ir_to_mesa_visitor *v,
 		   ir_to_mesa_src_reg *r)
 {
-   struct ir_to_mesa_dst_reg dst_reg;
-   ir_swizzle *swiz;
-
+   /* The LHS must be a dereference.  If the LHS is a variable indexed array
+    * access of a vector, it must be separated into a series conditional moves
+    * before reaching this point (see ir_vec_index_to_cond_assign).
+    */
+   assert(ir->as_dereference());
    ir_dereference_array *deref_array = ir->as_dereference_array();
-   /* This should have been handled by ir_vec_index_to_cond_assign */
    if (deref_array) {
       assert(!deref_array->array->type->is_vector());
    }
@@ -1638,38 +1635,7 @@ get_assignment_lhs(ir_instruction *ir, ir_to_mesa_visitor *v,
     * swizzles in it and write swizzles using writemask, though.
     */
    ir->accept(v);
-   dst_reg = ir_to_mesa_dst_reg_from_src(v->result);
-
-   if ((swiz = ir->as_swizzle())) {
-      int swizzles[4] = {
-	 swiz->mask.x,
-	 swiz->mask.y,
-	 swiz->mask.z,
-	 swiz->mask.w
-      };
-      int new_r_swizzle[4];
-      int orig_r_swizzle = r->swizzle;
-      int i;
-
-      for (i = 0; i < 4; i++) {
-	 new_r_swizzle[i] = GET_SWZ(orig_r_swizzle, 0);
-      }
-
-      dst_reg.writemask = 0;
-      for (i = 0; i < 4; i++) {
-	 if (i < swiz->mask.num_components) {
-	    dst_reg.writemask |= 1 << swizzles[i];
-	    new_r_swizzle[swizzles[i]] = GET_SWZ(orig_r_swizzle, i);
-	 }
-      }
-
-      r->swizzle = MAKE_SWIZZLE4(new_r_swizzle[0],
-				 new_r_swizzle[1],
-				 new_r_swizzle[2],
-				 new_r_swizzle[3]);
-   }
-
-   return dst_reg;
+   return ir_to_mesa_dst_reg_from_src(v->result);
 }
 
 void
@@ -1684,6 +1650,23 @@ ir_to_mesa_visitor::visit(ir_assignment *ir)
 
    l = get_assignment_lhs(ir->lhs, this, &r);
 
+   /* FINISHME: This should really set to the correct maximal writemask for each
+    * FINISHME: component written (in the loops below).  This case can only
+    * FINISHME: occur for matrices, arrays, and structures.
+    */
+   if (ir->write_mask == 0) {
+      assert(!ir->lhs->type->is_scalar() && !ir->lhs->type->is_vector());
+      l.writemask = WRITEMASK_XYZW;
+   } else if (ir->lhs->type->is_scalar()) {
+      /* FINISHME: This hack makes writing to gl_FragData, which lives in the
+       * FINISHME: W component of fragment shader output zero, work correctly.
+       */
+      l.writemask = WRITEMASK_XYZW;
+   } else {
+      assert(ir->lhs->type->is_vector());
+      l.writemask = ir->write_mask;
+   }
+
    assert(l.file != PROGRAM_UNDEFINED);
    assert(r.file != PROGRAM_UNDEFINED);